New borate compound and method of preparing same



oct. 19,1937. y H. B. SUHR 2,096,266

NEW BORATE COMPOUND AND METHOD OF PREPARING SME Filed Feb. 8. 1935 4sheets-sheet. 1

SYSTEM ma B6 o1- JBoJ-Hzom 55C 1 4 o l vfi" l//l 9 9; l/ l l 60 y 0*@ fa Hmon-mmo Oct. 19, 1937. H. B. sul-IR 2,096,266

.NEW BORATE COMPOUND AND METHOD 0F PREPARING SAME Filed Feb. 8, 1935 4Sheets-Sheet 3 SYSTEM Nus., ,445505-120 a 50C f moLs H3303 PER Joao nonWATER zo I um 54o,- omc I"ml-f M2340-, PER :ova non swmen gmcwm Oct.19,1937.

H. B. sul-I R Filed Feb. 8, 1935 4 Sheets-Sheet 4 123 560 RIN kmhw n.32son; mmm nommx n TIOL` Na.: B407 PER 1000 MOL 5 WHTER Patented Oct.y 19,1937 UNITED STATES NEW BORATE COMPOUND AND METHOD 0F PREPARING SAMEHenry Bruno Suhr, Trona, Calif., assigner to American Potash & ChemicalCorporation,

Trona, Calif., a corporation of Delaware Application February 8, 1935,Serial No. 5,539

12 Claims.

` This invention relates to a new borate compound and to the method ofpreparing same.

j I have discovered that there can be formed a new ysodium boratecompound which contains three molecules of sodium oxide v(NazO) andeight molecules of borc oxide (B203) with ten molecules of water ofcrystallization. 'Ihe prob able formula of this compound is This newborate thus contains a ratio of NazO to B203 which lies ybetween thevcorresponding ratio for the tetraborate, Na2B4O7, and the pentaborate,NazBmOie, which latter are well known compounds.v Heretofore, it hasbeen considered that there existed only one sodium borate, namelyNa4B1oOr1m5I-I2O, between the tetraborate and the pentaborate. Thissodium borate is reported by V. AAuger/(Comptes Rendu, 180, p. 1603) tobe 'formed at temperatures in the neighborhood of the boiling point ofwater and has not been reported as existing in contact Vwith solutionsat lower temperatures. The various solubility diagrams of the systemNazO--BzOs--I-IzO at temperatures of 30 C. rand 60 C., for example,(Inorganic and Theoretical Chemistry, by J. W. Mellor, vol. V, page 67)show only pentaborate as a solid phase between tetraborate and boricacid. I have found, however, that there exists an additional stablesolidphase, namely This new compound possesses considerable valuein theglass and enamel industries due to its high boric oxide content. It is ageneral practice in many glass and enamel batches to utilize mixtures ofsodium tetraborate or borax and boric acid to supply the boric oxidecontent when it is desired to do so without toov greatly increasing thesodium oxide content. By using my new compound the desired boric oxidecontent may be supplied while maintaining the sodium oxide suitably low.This new compound is also an excellent n water softener and kmay beincorporated to advantage in detergents.

vrItis, therefore, an object of this invention to provide la, new sodiumborate compound which possesses )value fork use in Variousindustries.

It is my belief that this new borate compound has not been previouslydiscovered, because (l) it has a very slow rate of crystal growth, and(2) at the 'temperatures and conditions of concentration at which thisnew compound exists as a stable phase other sodium borate compounds tendto precipitate unless special technique is utilized to cause aprecipitation of this new borate, which is a real stable compound. Forthis reason, di-

f culty is encountered in preparing the vnew comto provide a method bywhich this new borate compound may be crystallized from a solution.

The present invention, together with various additional objects andadvantages thereof will best be understood from a description of thepreferred compound, and a preferred process or processes for producingsaid compound. For this reason, I have hereinafter described, withreference to the accompanying drawings, a preferred process or processesfor producing the compound.

In the drawings:

Figure l is a solubility diagram of the system NazBqOfz-HsBOs-HZO at 35C., the ordinates representing the mols of HsBOs per thousand mols 0fwater present and the abscissa the mols of Na2B4O'7 per thousand mols ofwater present.

Figure 2 is a similar solubility diagram at 35 C., in which the solutionat all points is saturated with sodium chloride, so that the systemincludes the ingredients the concentration of sodium chloride, however,does notappear on the diagram, the data therefor being listedseparately.

Figure 3 is a solubility diagram of the system NazBloq-HBBOB-md Similarto that of Figure NaaO-BzO'a-HzO at some temperature at which saidcompound is stable.

To this end, I have shown the solubility diagram of the systemNaaBiO'r-HSBOx-Hzo at 35 C. in Figure 1. In a diagram of this nature,the curves represent the compositions of saturated solutions of allcompounds or mixtures of compounds preparable from boric oxide andsodium oxide between and including the compounds sodium tetraborate andboric acid. The composition of every saturated solution between one ofthe tetraborate and one of boric acid which may be produced from sodiumoxide, boric oxide and water, can also be produced from sodiumtetraborate, boric acid and water, and all of these solutions at 35 C.are located on the curve |-2-3--5 of Figure l. The various peaks orbreaks in the curve represent the points at which il Change occurs inthe solid phase which separates 2 upon concentration. Thus, fromY l to2, boric acid may be caused to crystallize by concentrating any solutionhaving a composition lying along Y the curve.I-2, while from 2 to 3.sodium pentaborate decahydrate is the solid phase which crys- Ytallizes out. Likewise, from 4 to 5Y sodium tetraa in the ratio of 3:8(i. e. 3Na2B4O7z4I-I3BO'3) were V added to the solution, the compositionupon .anal-- .ysis would be found VtoV lieV further to the right,

borate decahydrate or borax is the crystallizing solid phase. It willnot alwaysV be possible to crystallize a solidV phase indenitely froma'given solution by concentrationV as the crystallization of the solidphase may cause'such a change in the composition of the remainingsolution as will cause a new solid phase to vappearuponiurtherconcentration. Y Y i VAs previously noted, the curves I-'2-3-45represent all. saturated solutions which can be prepared from sodiumtetraborate, boric acid andY water. The solutions' represented byallpoints outside of the curves Ir-2-3-4-5 'areY either supersaturatedsolutions or sludgeswhile Y those inside the curves are unsaturatedsolutions. Y

I. OnA the several figures 'ofthe drawings there have been plottedcertain lines which are designated as the congruency lines for variouscompounds.` on the solubility diagram. These congruency lines might alsobe calledl composition lines. For instance, the compound Na6B1eO2v maybe considered as consisting of 3 mols of NazBlOv and 4 mols of HsBOa.More correctly, as 3 mols of Na2B4O5i and 2 mols of B203. Referring nowto Figure 2, if a mixture of 3A mol. of yNa2B4O7 and 1 mol. of HaBOa'were placed in water (in say, 1,000 mols of water), the composition ofthe resulting unsaturated solution would lie 'along the line markedcongruency line (of NasBieOzv) on saidr figure. If a further smallquantity Yof the mixture which Vcontainedv NazO and B203 iNacBisOzvLlOHzO y Further additions of thel compound Y v.

NasB16O27.10I-I2 1 would not change the composition of the solution.'

However, if thetotal mixturewere analyzed, i;'e., the solid material andthe liquid (commonly called sludge), its composition would be 'found tolie further to 'the right-along the so-called com- Mols V'II3BO3 1,000Na2B407 750 H2O 1,000V

position or congruency line. The termination of this congruency line isxed by the compositionV of the saititselr, i.' e. of Nanreozmlomo. 1f weconsider aquan'tity of said compound, forexample, 250 gram molsofNaeB1sO2'i-10H2O, this weight of material may be expressed in thefollowing' terms:

If this composition were plotted 0n a diagram,

. iS NasBisOlalOI-IZO.

As a matter of interest in the specic case similar tonigurs 1, 3 :orLanci this point connected with Vthe origin r0 by ,a straight une, the Ycongruency' line would be immediately'fxed and determined.'V TheY nal`pointL `just referred to,V f l. f

i. e. the right-hand termination of this line,'is also known asfthecrystallization starting point of the compound in question, which inYthisV case The importance ofthe congruency'line readily understood whenthe congruency line is considered in connection with vFigure In thisin'- stance,V the system HaBOa-NazBiO'zi-Hw, free Y of sodium chlorideis plotted. Now, if we go back and retracethe former explanation, we ndan entirely differentcondition, than the one just explained for thesystem saturated at 35C. with sodium chloride (Figure 2) i f Asa smallquantity of compound NaeBisOzv is placedv in the solution, thecomposition of the solution so produced will progress out `from'theorigin Oalong the e NasBieOzfr congruency line until the concentration'Vbecomes sufficiently great to intersect the solid curve Y4-'-ll.However, unlike the previous example, further addition of thecompoundwillgnot,Y

result in the composition of the solution itself re? maining constant.On the contrary, Y,the added compound NaeBieOzmlOI-IzO will'immediatelystart to decompose, and part of its constituents'will-go intosolutionwhile the remaining part will pre-1 Ycipitate-not as.'NasBieOz'nlOHzQbut as com-v mon borax NazBliO'LlOIV-I'zO. If wecontinue Vto Y*add the compound Na6B16O27-lQH2O, the compo' Y sitionofthe solutionfwill progress along the curve 'Fr-4in the direction ofpointA, becoming itseli` i' Y enriched in YHBOa and Vprecipitating ahuge crop of NazBiOmlOI-IzO. 'Ir'hisfis another way 'of say- Y ing'thatthe compound.Naswomlomo is not stable or congruent with its ownsolution in the absence of Vsodium''chlorideat 35` C.' In other words,'if this new compound at sucha temperature is treated with water itdecomposes, precipitating borax` andforming Ya solution of high .i

boric acid content.` It is not `until, this decomposition has proceededto theY extent thattheY solution contains over 60Vmols of HaBOa andsomething over 17 mols'of Na'zrBiO: that this de-j compositionwillcease.VV When-this condition has been reached, the solution will havereached'VV point 4 of Figure l, which isV saturated withY the ,newcompound and at the Sametime with borax.V

, The Vcorollary ofV the foregoing is evident; namely, that if asolution is rmade up to contain Y Naz() and B203 inV the ratio of3:`8and thisfscilu- Y. tion cooled to, orconcentrated at, 35 C., the comNpoundNaeBieOr/.lOHzO will not beV precipitated;

but, on the contrary, the precipitate will consistV only of 'commonborax (Na2B4O7.10I-I2O) The .I

only way in which the new compound can be 'pre-Y pared at 35",; C.VY inthe absence Vof sodium chloride` is 'by'causing it to precipitateV froma solution which does vnot Vhave .Y the v,compositionofr 3Na2`0z8B2vO3,but rather fromY a solution which has the 'composition'expressedV bypoints Y along the curve 3'-f4`, the' midpoint of which has (forexample) the ratio ofiBNazrOrllBzOa.

In many cases it is desired to know what compoundwill crystallize fromYa given solution, ing

what quantity and'vvhatthe compositionof the remaining mother liquorwill'be. nature can be Vdetermined from a set of curves` Y 'of thistype. 1f the solutionis a saturatedone,

it will, 'ofY course, lie directly on theV curve and crystallization canbe effected therefrom by con' Data of this Y centrating theisolution.VAs a' result .ofsuch Vconl centration, the composition of 'theremaining sosolid phase' will begin to crystallize.

lution will move along the curve away from the intersection of saidcurve with the congruency line of the crystallizing compound until abreak vin the curve is reached; such a point will represent a point atwhich the solution becomes saturated with an additional solid phase andthis If this peak or break in the curve is between the congruency linesfor the two compounds with which the solution is then saturated, furtherconcentration under equilibrium conditions will not cause any change inthe composition of the solution. It will therefore remain constant andthere will be precipitated a mixture composed of the two compounds inproportions to give a composition corresponding to that of the solution.If this peak or break is outside of the area dei-ined by the twocongruency lines, further concentration will cause the composition ofthe solution to move along the branch of the curve representing thesecond compound and that compound alone will be the crystallizing solidphase. Thus, in Figure 1, if a solution lying on the curve 2 3 betweenthe intersection of the congruency line for and the point 3 isyconcentrated isothermally, crystallization of Na2B1oO1e-10H2O willresult until the mother liquor composition reaches the point 3. Atthatpoint the solution is saturated With Na2B1oO16.10H2O andNaeBlsOz'nlOHzO. Since the point 3`is between the congruency line forthe lattercompound and that for NazBioOls. k10H20 further isothermalconcentration will cause the precipitation of a constant compositionmixture of the two compounds in those p-roportions in vwhich they existin the solution. No change in the composition of the solution will occurunder equilibrium conditions. If, however, a solution lying on the upperportion of the curve 4 5 is concentrated, crystallization ofNagBLiOr/.lOHzO takes place, and the composition of the mother liquorproceeds along the curve 4 5 until the point 4 is reached. At that pointthe solution becomes saturated with NaeB1sO2'1-10I-I2O. Since this pointis on the same side of both' the congruency line for NaBisOzmlOI-IZO andthat for Na2B4O7.102O, this point is not an end point ofcrystallization. Further concentration thus will cause the deposition ofNasBieOzmlOHzO only, and the composition of the solution will proceedalong the curve 3 4 until the point 3 is reached. As already noted thislatter point is an end point of crystallization.

If the solution is an unsaturated one, concentration thereof will causethe composition to move outward along a linepassing through the origin 0and the point representing the composition of the solution.Crystallization can be effected as soon as suicient concentration hastaken place tocause the solution to become saturated. Crysvtallizationfrom a solution so concentrated will proceed as described in thepreceding paragraph. When the solution is a supersaturated one or is asludge of one or more metastable solid phases, crystallization can beimmediately effected by 4seeding with the stable solid phase andagitating or in some cases by agitating alone. The crystallization pathwill be along the line drawn through ythe point representing thecomposition of the solution or mixture and the point representing thecomposition of the crystallizing stable phase. Thus, for example,referring to Figure 4, if the compound NasB1eO21-10H2O is ther stablesolid phase, the crystallization path will be along a line drawn throughthe point representing the composition of the solution or mixture and apoint representing 1000 mols of HsBOg and '750 mols of Na2B4O7 per 1000mols of water, which is a point considerably beyond the limits of theplots shown. Since a given phase is the stable solid phase only so longas the path of crystallization intersects the portion of the curve forwhich that compound is the stable solid phase, the field which includesall solutions and/or mixtures from which a compound can be crystallizedis defined by lines drawn through the terminal points of that section ofthe curve for which the desired compound is the stable solid phase andthe crystallization starting point for that compound.

f Referring to Figure 4, this field for the kcompound NasB1sO2'z-10I-I2Ois partially defined by the lines 8 32 and 9 33, which are portions ofthe lines drawn between the terminal points 8 and 9 of the curve 8 9 andthe crystallization starting point for NaeBieOytlOHzO. All solutions orsludges lying in the area to the right of the curve 8 9 and between thelines 8 32 and 9 33 will deposit NaeB16O2v-10H2O upon crystallization,when the nal solution, at C., is saturated with respect to NaCl. In somecases, there also exist one or more metastable phases which maycrystallize from a given solution if stable equilibrium is not attained.This is true in the case of NasBieOzmlOHzO, sodium pentaboratedecahydrate and sodium tetraborate decahydrate being metastable solidphases within the field for which NaaBisOzmlOIhO is the stable solidphase. In such cases, if a metastable phase does crystallize, it willbecome converted to the stable phase merely by agitation for asufficient period of time.

Prior to the discovery of my new compound, the solubility curve for thissystem at 35 C. was believed to extend to the point 3a, as shown indotted lines on Figure 1. Otherwise stated, the sodium pentaborate eldwas believed to extend from 2 to 3a and the sodium tetraborate fieldfrom 3a to 5. I have found, however, that sodium pentaborate and sodiumtetraborate exist only in a metastable condition from 3 to 3a and 3a to4, respectively. Actually, there exists in this system at this andhigher temperatures a new stable compound which has the formula3Na20.8B203.10H2O i. e. NasB1sOz7-10H2O. This ne-w compound is stable incontact with all solutions existing along the branch of the curve 3 4 at35 C.

The preparation of my new compound requires special precautions andprocedure because it is not congruent with its own solution at alltemperatures. This is readily apparent from Figure 1, which shows thecongruency line for NaeBieOzv, it being apparent that this line does notcross the curve 3 4 representing the solutions with whichNaeB1sO27.10H2O is stable, at any point. I have also found that this newcompound crystallizes only very slowly at 35 C. In cases of this nature,where a desired compound is not congruent with its own solution, it isthe usual practice to prepare the compound by crystallizing it from asolution with whichl it is stable. In the present case, for example, thenew compound NasBieOm can be prepared by iirst preparing a solutionhaving a composition on the curve 3 4 and then cooling or concentratingthis solution. With this method, however, only very small amounts of thenew compound can be obtained as the range of compositions of solutionsVwith which the new compound is Ystable is very limited in pure solutionsatf35" C. Also, the tendency for the compound to crystallize is so smallVthat the compound is attainable only with extreme difficulty at thistemperature by ordinary or usual methods from.l Y solutions free fromextraneous substances, such as NaCl. Y

To overcomethese diliculties and provide successful procedure forpreparing my new compound is one of the objects of this invention. Thisobject has been accomplished in accordance with this invention in anumber of ways, based upon certain Yfundamental discoveries whichv Ihave made.V YI have-found that thesolubility of the new compound isdecreased and the range of solution compositionsV with which it isstable isincreased by the presenceV of sodium chloride,

I have also found that the eld of the'new'corrl-` y,

pound is greater at higher temperatures. Based upon these discoveries, Iprefer to prepare the new compound by causing it to crystallize fromy asolution which is saturated with sodium chloride or which is atatemperature above 35 C., or

which satisesboth of these conditions;

The effect of the presence of sodium chloride is evident from Figure 4,which shows the solubility diagram `for the system YNa2B407--H3BO3-NaCl-H2O 'Y at 35 C. with all points saturated withsodium chloride superimposed on the diagram for the chloride free systemNazBiOv-HsBOz-Hzo at the same temperature. It will be noted that thesolubilities of all phases in the system are appreciably reduced by thepresence of sodium chloride. The greatest effect of the presence ofsodium chloride, however, is the large increasein the length of thecurve for which NasB1eO27.10I-I2O is the stable solid phase and theattendant decrease in the 'length of the l\Ta2B4O'1.10H2O portion of thecurve. The increase ink the Na6B1sO27-10I-I2O iield is so great thatthis compound is now congruent with its own solution when saturated withNaCl. Asin the case of the diagram of Figure 1, the dotted lines from 8to 8a and from 8st to 9 represent the diagramas it was believed to existprior to the discovery of my new compound. Likewise, sodium pentaborateand sodium tetraborate are metastable along the curve 8-8a-,9. Theincrease in the range of solutions with which the compoundNasB1sO2v.l0I-I2O is stable is apparent from the increased length of thecurve 8-9 over the curve 3-4 of Figure l.Y This is especially noticeablefrom the superimposed curves of Figure 4. Y Y

All points are saturated with NaCl in the curve of Figure 2 but thiscomponent is not plotted. The NaCl saturation values corresponding withthe several points on this curve are approximately as follows:

Stable solid phases Nazcznzoills1 gzoClJs/looo NaCl, HaBOa (point 6)`56. 6 NaCl, HaBOaNazBmOieJOHZO (point 7) 55. 8 NBC] Na2B10O16.10HNaB1O2-1.1OH2O 55. 7 (POID 8). NaCl NaqBw021-l0H2O (point 8b) 54.7 NaCl,N36B1a027.10H2O (DOlIlt 8) 54.4 NaCl, NtBleOeLlOHzO, N32B407 10H20 55. 1(Point 9). NaCl, NaQB4O7.lOH2O'(point l0) 54.0

The effect of temperatureV on the solubility of the other solid phasesisk quite marked, whereas the solubility of the new compound doesnotchange greatly with change oftemperature.

Therefore at 50C., as shown inV Figure 3, the field of the new compoundhas greatly expanded ink size over that of the 35 isotherm due to thegreatly increased solubilities ofthe adjacent compounds Na2B1oO1e.10H2Ot and" Na2B4O7.1H2O.

However, the lcompound NaeBieOz'zglOI-IzO is not congruent with its ownsolution at 505Y C., though it becomes so at a. slightly highertemperature and remains so 'atV higher temperatures. There Yisanadditional eifectof' temperature on the'formation of the'new compoundwhichis not'apv parent from the solubility diagram, namely, theV eiecton therate of crystal formation'and crystal At lower temperatures,crystals ofi consequentlyY crystal growth Vat higher tempera- K turesis, improved. d

The preparation of this new compound inkpure f formv is additionally*complicated by the fact that sodium pentaborate decahydrate and sodiumtetraborate decahydrate tendV to separate as met-- y astable solidphases fromy a large range of solutions' from which NasBisO2'z-10I-I2Oshould ultimately crystallize as the stableI solid phase. Thesolubilities of thesemetastable solid phases change greatlywithtemperature, as stated above.

For this reason, I have found it desirable to efi feet a rapidseparationof the mother liquor from the crystals of NaBisOzmlOI-IZO when thepreparation thereof has been accomplished at temperatures aboveatmospheric. YIf the separation is not sufficiently rapid, Vcooling andevaporation of the mother liquor may occur and there exists a fairlypositive tendency-for either sodium pentaborate or ,sodium tetraborateYto crystallize therefrom. This is increased by the great tendency forthe newrcompound Na6B1eO2v-10H2O to supersaturate. This tendency issorpronounced that complete equilibrium,fi. e. release ofsupersaturation, is diiicult to obtain.V Asma consequence, the motherliquors at higher temperatures often tend to be very viscous duey `tothehigh y,content of dissolved salts resultingV fromY the high solubilitiesof the metastable compoundsand supersaturation ofA my newcompound. Suchvis- Vcous liquors are difficult 'to separate from the crystals ofNaeBieOzmlOHzO. To overcome this difliculty, I accomplish the separationof the crystals and mother liquor when the production has been executedat higher temperatures by rapidly introducing a large quantity of Vcoldwater into the mixture of motherk liquor and crystals and then lteringorV otherwise separating the crystals from the liquor. By employing aYsufcie'nt quantity of added water, saturationwith the metastable phases,sodium pentaborate decahydrate and sodium tetraborate decahydrate uponcoolingis prevented, and it is possible to separate the crystals ofNasB15O2v-10H2O in substantially pure form. Cold water is preferablyemployed as the rateof solution of the comtemperatures.Y Y I poundNasBisOzmlOHzO is much'less .at lower Y A numberA of methods ofpreparingV the newV compoundwillbe evident from the ydiscussion givenheretofore, but one which I have found especially satisfactory involvescrystallization vat an elevated temperature. As has been noted inconnection with the diagram of Figure 3, the

new compound becomes congruent with its solu- Y tion Vatsome temperatureslightly higher thanY 50 C. andremains so at higher temperatures.VCrystallization at higherV temperatures, there;-

fore, permits the use of solutions containing Na2O and B203 in the ratioin which they exist in the desired compound, i. e. the ratio I,therefore, dissolve boric acid and a free sodium oxide containingcompound in such proportions that there is produced a concentrated,solution containing Na2O and B203 in the molecular ratio of 3:8. Anyfree sodium oxide containing compound maybe employed, but I find itpreferable to employ one which does not introduce additional elements orradicals. Thus, sodium hydroxide and the sodium compounds of boric acidhave been found satisfactory. Sodium carbonate may also be used. If asodium Vborate containing a greater ratio of B203 to Na2O than 8:3 isemployed, it will be necessary to add further free Na2O thereto in placeof the `boric acid. The solution so prepared is then tallize fromsolution, but as the temperaturein-` creases, the tendency for it tocrystallize increases appreciably. When the temperature is maintained inthe neighborhood of 100 C., the

'compound crystallizes fairly readily and no special precautions tofacilitate its crystallization are required. The crystals may beseparated from the mother liquor continuously as they form if it isconvenient to effect this separation in the hot liquid, but it willusually be found desirable f to effect the separation after thecrystallization cold than hot.

is complete. After the greater part of the solute has crystallized asNaeB1sO2m10H2O, the mixture of crystals and mother liquor is removedfrom the source of heat and a large quantity of cold water added quicklyto thereby dilute the mother liquor. Cold water is preferably added asthe new compound dissolves much less rapidly The quantity of water addedshould be sufficient to undersaturate the solution with the metastablesolid phase, sodium tetraborate decahydrate. Since this compound(Na2B4Of1.10H2O) will tend to form from a solution of the new compounditself, either as a metastable or stable solid phase, depending uponwhether the temperature is above or below that at which the new compoundbecomes congruent, re-crystallization can not be depended upon toeliminate any contamination therewith. It is thus essential that everyprecaution possible should be taken to prevent precipitation of ametastable phase.

Mention has already been made of the fact that another sodium boratecompound,

has been reported in the prior art literature. This compound has notbeen shown on the equilibrium diagrams of Figures 1, 2, 3, and 4 becauseit has not been known to form at temperatures below the boiling point ofwater. This compound, NafiBioOimIaIzO,A has been prepared by M. V. Auger(Comptes Rendu 180, p. 1603) by heatingy a solution containing sodiumoxide and boric oxide in the ratio of 2:5 or 1:2.5. I have found that mynew compound NaeB1oO27-10H2O may be prepared by boiling a solutioncontaining Na20 and B203 in a ratio of 3:8 or 1:2.67. Since the ratiofor my compound is so close to that for the compound Na4B1oO11.5I-I2O,seeding with this latter compound should be prevented when it is desiredto crystallize NaeBieOzmlOHzO at or near the boiling point as it islikely that NalBioOimHzO would crystallize if seeding therewith takesplace.

As an example of this method of procedure, I dissolve 100 grams ofborax, Na2B4Om10H2O and 21.6 grams of boric acid, HsBOa in 100 grams ofwater, and boil the resulting solution until the greater part of thedissolved constituents have crystallized as NaeBiOzF/.lOHzQ The motherliquor will have become quite viscous and crystallization is preferablydiscontinued when a small amount of mother liquor remains.Approximately, 100 cc. of cold water is quickly added and the crystalsseparated from the solution as quickly as possible to preventre-solution of the crystals.

This method above described utilizes the effect of temperature to securethe desired crystallization of the compound, and I have found that sucha method is satisfactory. If, however, it is desired for any reason tooperate at lower temperatures, I have devised a further method whichutilizes the effect of the presence of sodium chloride to facilitate thedesired crystallization. A solution having a composition lying on theportion of the curve 4-5 of Figure 4 between the points 34 and 35 isprepared and sufcient sodium chloride added to not quite saturate thesolution therewith when it has reached equilibrium at 35 C. The amountof sodium chloride added must allow for concentration due to the removalof water of crystallization of Na6B1sO27.10I-I2O upon crystallizationthereof. This solution is then agitated preferably with the addition ofseeds of NasB1cO27.10I-I2O. Due to the removal of water ofcrystallization with the NasB1sO2'1-l0H2O, the solution Will undergoconcentration and maintain a state of supersaturation with respect toNafBifsOzf/.IOHzO` until equilibrium is reached. Since .35 C. is notgreatly above room temperature, contamination with metastable phases asa result of cooling is not very likely to occur. After crystallizationof NaaB1O27.l0I-I2O has proceeded to the point where the composition ofthe mother liquor falls within the area bounded by the curves 8-8a-9,the solution becomes unsaturated with these metastable phases and theircrystallization can no longer occur. In fact, they will tend tore-dissolve, if already present. For this reason, I prefer to agitatethe mixture of crystals and mother liquor for an hour or so aftercrystallization has apparently ceased, in order to re-dissolve anymetastable phases which may have separated in the early stages ofcrystallization. Contamination with sodium chloride, except thatcontained in adhering mother liquor, is alsoy avoided by holding theNaCl concentration below that value which represents saturationtherewith at the end point or equilibrium point of the crystallizationreaction.

The curves of Figure 4 are the solubility curves l-2-3-4--5 of Figure lfor the system Na2B4O7-H3BO3-H2O at 35 and 5 1-3-8-I0 of Figure 2 forthe systemV at 35. From the superimposed curves the magnitude of theeffects caused by NaCl in the System NazBsOI-HaBOa-Hzo be- Y saturatethe mother liquor.

path for any'given solution in this field will be the i these lines, andthey define ther field within which lie all solutions' or sludges fromwhich NasB1eO27-l0H2O can be crystallized in pure form when sufficientNaCl is present to substantially The crystallization extension-of astraight line drawn through the crystallization starting point and thepoint representing the Ycomposition of the initial solution fromwhichfcrystallization is to be effected. I'he intersection of this linewith the curve 8 9 is the composition of the mother liquor if noconwiththe curvesof Figure 4. `As previously set forth, any saturatedsolutionrwhich upon addition 1 of sodium chloride will .crystallizeNa6B1sO27-10H2O and give a mother liquor having a composition somewherevon, the curve 8 9 of Figure 2 or Figure 4 can be employed in thisprocess. Consequently, any solution of Na2B4O7 and HaBOa in water lyingbetween the lines 8 32 and 9 33 and between the curves 8 9 and 4 5 willyield Na6B1sO27-10I-I2O when sufiicient sodium chloride is added tosubstantially saturate the mother liquor. The yield will vary directlywith the distance between the solution composition point and the curve 89 along the crystallization path. Consequently, the greatest yields willbe obtained by starting with a solution nearthe intersection 34 of theline 8 32 and the curve 4 5. Such a solution is one containing 9.1 molsof Na2B4O7 and 28.6 mols of I-IsBOa in 1000 mols of H2O. WhenV such asolution is treated 'with 53-54 mols of Na2Cl2 at 35, pureNaeBisOzmlOHzO Y will bedeposited when equilibrium is reached. At thestart of crystallization a metastable phase of either sodium pentaboratedecahydrate or sodium Y tetraborate decahydrate may crystallizeinaddition( to NaeB1sO2v.10H2O, but when equilibrium is reached anymetastable phase so crystallized will haveubecome converted to thedesired compound NasBieOzmlOHzO. For this reason, it is desirable thatsuiiicient time be allowed to permit 5 equilibrium to becomeestablished. From the starting solution used in the above exampleapproximately 15.6 mols of Na6B16O2v.10I-I2O are obtainable. v Y

While this method of procedure has been described in connection withcurves at 35 C., it is equally applicable at any temperature at whichthe desired compound, NasB16O2v-l0I-I2O, has a eld of stability. Themethod of procedure is the same at any such temperature and thecompositions of solutions required canbe readily determined from-thesolubility curve at the desired temperature. Y i

Since the congruency line for the new compound intersects the field ofstability thereof in the system containing sodium chloride atsaturation, as shown by the diagram of Figure-2, the second or fcoldmethod of preparation may be employed by starting with a solution madeup of stoichometric quantities of boronV oxide and sodium oxide andcontaining just enough sodium chloride to substantially saturate themother 'new compo-und is produced.V Y however, that equilibrium beessentially established as one of the metastable solid phases,`

liquor therewith. The quantities of sodium'tetrborate, boric acid andwater required to make up such a solution areV shown by the coordinatesof the point of intersection 'of the 'Y NasB'1sO2m10H2O Y Ycongruencyline Ywith ,the curve 4 5 ofuFigure 1. Such a solution rwould becomposed of 5.5 mols of sodium tetraborate decahydrateY and 7.2 mols of'boric acid. The NaClY required to` saturate'the mother liquor isbetween'53 and 54 mais of Nason in V1000 mois orwater.- As mY the caseofthe previous example, crystallization of NaeBisOzmlOHzQ fromV such `asolution will start .upon addition of they sodiumr chloride and vwillcontinue until equilibrium is reached and` any precipitated metastablephase is convertedA to NaeBieOzmlOI-IzO.

It is also possible to Vproduce my newy borate j compound by a solidreaction or conversionwhen a sludge composed of stoichiometricquantities to dissolve all of the solids reacting is agitated attemperatures above about 51 C. The speed of reaction or conversion is`appreciably greater at higher temperatures.

of borax and boric acid with insuiiicient water 25"V Contamination witha metastable solid-r phase -upon rapid cooling of the mixture ofcrystalsV andmother liquor must v. be avoided in this reaction as in thecase of the Y high temperature process described above. Contaminationsof this nature may be conveniently prevented by adding excess cold waterupon ccmmother liquor.

All of the methods Vheretofore set forthY are substantially batchprocesses and consequently the production thereby may be consideredlimited. vA continuous method of producing my compound comprises addingNazO.V B203k and H2O is stablein contact with the-starting solution.

In this method, NazO, B203 and H2O are added continuouslyuntil thedesired quantity of the It is necessary,

NazBiOmlOHzO or Na2B1oO1s.l0I-l20 may be precipitated and remainunconverted. Referring to Figure 4, production of the new compound byYthis vprocess is accomplished by taking a solution represented by anypoint von theV curve Vpletion of the reaction to sufficiently; dilutethe 8 9 Vort-ll, preferablyrnear the center thereof, adding NazO,VBz'O'aVand H2O thereto in the proportion inwhich they exist inNaeieoaionzo ly applicable when operating at higher temperatures asV therate of crystal growth of NaeBicOz'nlO-IO is considerably greater'Y athigher temperatures. Various free sodium. oxide andY boron oxidecontaining materials may be used in such a process.v For example, boraxand boric acid may be clis-KV solved in water to form the original orbasic solution, Sdiurnchloride .being added to saturate ther y Inproducing NaeB1eO2m10I-I2O from this basic solution by the addition ofNa20, B203 and H20 ytheretol it is essential that. these ingredients beadded substantially in the proportions in which they exist inI\Ia6Bie027.10H20, so that the composition of the solution remainsysubstantially constant. Fluctuations in the amount of water added arepermissible so long as the composition of the mother liquor remainswithin the field from which'NasBisOzmlOI-IzO will crystallize. Ifconcentration occurs, vfor example, the composition of the mixture willmove away from the origin 0 of the curve and such concentration must belimited so that the solution composition does not reach a point outsideof the field defined by a line drawn through the point I3 and theNaB1602f/.10H20 crystallization starting point. When dilution occurs,the solution, of course, becomes unsaturated and NaeB1e027-10I-I2Oalready crystallized will be re-dissolved until saturation is againreached. If the operation is carried out under conditions such that.NaB1sO21-10I-I2O is congruent with its solution, then continueddilution can only cause continued resolution of the Na6B16O2v-10I-I2O,but can not cause precipitation of any other phase. If congruency willnot occur, dilution must be controlled'so that resolution ofcrystallized Na6B1602m10I-I20 will always produce a solution at or aboutthe transition point between sodium tetraborate decahydrate and the newcompound.

The proportion Vof water, sodium oxide containing component and boricoxide containing component required to produce the new compound from agiven basic solution can be determined from the equation representingthe reaction which occurs to produce said compound.` For the use ofborax and boric acid, the equation vthe solution, such as byevaporation, should be elected to maintain the composition of thesolution within the NasB1aO2f/.10H2O field. It is also vpossible toreduce the amount of concentration t required when using hydrated boraxby employing metaboric acid, HBO2, in place of boric acid. 'I'hereaction then is as follows:

This new borate compound has especial value in the glass and enamelindustries. In recent years, it has become standard practice to employsmall quantities of boron oxide in both glass and enamel batches, asthis constituent has been found to impart improved qualities to thefinal products. Because borax is the most common commercial form ofboron compounds, it has been largely used to supply the desired boronoxide component in glass and enamel batches. In many cases, however, theadditional sodium oxide supplied as part of the borax added isundesirabi-e, and for this reason where increased quantities of boronoxide are desired a mixture of borax and boric acid is employed. Becauseof its higher ratio of B203 to N220 my new compound is especiallysatisfactory for use in glass batches.

While the particular compound and method of preparing the same hereindescribed are well adapted to accomplish the objects of the invention,various modifications and changes may be made, all coming within thescope of the appended claims.

What I claim is:

1. A new product comprising a sodium berate compound resulting from thecrystallization from solution of a sodium borate with water ofhydration., in which the ratio of Na2O to B203 is substantially 3:8.

2. A new product comprising the hydrated sodium borate compound having acomposition represented by the formula NasB1e02i-10H20.

3. A new karticle of manufacture comprising a sodium borate compoundcontaining NazO and B203 in the ratio of substantially 3:8 with water ofcrystallization.

4. The method of preparing a sodium borate composed of Na20 and B203 inthe ratio of about 3:8 which comprises preparing a solution containingNa20 and B203 in their stoichiometric proportions in said sodium borateand essentially saturated with respect to sodium chloride, andconcentrating said solution at a temperature above about 35 C.

5. The method of preparing the compound NasB1s027-10I-I20 whichcomprises preparing a solution containing Na20 and B203 in proportionsto give a composition within the NasBisO27-l0H2O eld, adding sodiumchloride there-to in quantities at least as small as that quantity whichwill saturate the equilibrium mother liquor, and agitating the mixtureto bring to equilibrium.

6. The method of preparing the compound NasBie027.10H2O which comprisespreparing a solution containing Na20 and B203 in proportions to give acomposition on the NasB1sO27.10I-l20 s01- ubility curve at any desiredtemperature, adding free sodium oxide and free boric oxide containingcompounds and water simultaneously in such proportions that the Na20,B203 and water added are in the ratio of 3:8: 10, and agitating tosecure conversion to NaBisOzmlOI-IzO.

7. The method of preparing the compound N asB16027-10I-I20 whichcomprises preparing a solution containing Na20 and B202 in proportionsto give a saturated solution on the NasB16O27.10H20 portion of thesolubility curve for the system Na2O--B203-H20 or Na20-B203-NaCl-H20 atany desired temperature, adding a rmixture containing free Na20, freeB203 in the proportions in which they exist in Na6B1e02m10H20,controlling the water content of the reaction mixture so that thecomposition thereof remains in the NaeBisO2v-10H20 field, maintainingthe temper- Vio ature 'substantially constant when loperating at atemperature at which the desired compound is not congruent With itssolution `and agitating the reaction mixture to secure conversion toNasBuO27.10H2O. Y n

8.Y The method of preparing the vcompound NaGB1s02r/.1GH20 whichcomprises preparing a so- Y lution containing Na20 and B203 inproportions to give a saturated solution on the Na6B1s027.10I-I20portion of the solubility curve Vfor the system a temperature above theminimum temperature at which congruency of NaeB1s027`.10I-I20 Wthitssolution occurs, adding a mixture containing free Na20, free B203 in theproportions in which they exist in NasB1e027-10H20, controllingthe watercontent of the reaction mixture so that the composition thereof remainsin the Na6B1s021-10H20 eld maintaining the temperature above the 10W-est temperature at which 'congruency of the Water content ofthe reactionmixture by controlling the hydration of the reaction components employedto'supply the Na20 and B203 contents so that the compositionthereofremains in the YNaB1O2m10H20 eld, maintaining the temperaturesubstantially constant Whenroperating at a temperature at Which theVdesired compound is not congruent with its'solution and agitatingthereaction mixture to secureV conversionto 10. The'method of preparing aYsodium borate Y Y composed of Na20 and B203 in the ratio of about 3:8which comprises preparing a solution containing Na20 'and' B203 in theirstoichiometric* proportions in said sodium borate and'concentrating saidsolution ata temperature'Y above about 51 0.1

chloride to,Y and effecting crystallization or" NasB1sO27.'l0Hz0 from,a' solution containing free Na20 and B203 in'such proportions as Willicause the composition of the final mother liquor to correspond to apoint Within the'Na6B1e'O2m10I-I2O field of stability as dened by theNazo-V'mog-Naci-mo solubility diagram at the desiredtemperature.

Y12. The method of.y preparing the .compound v11. The method .ofpreparing the compound Y NaB1s02v-l0H2O which comprises adding'sodiumNaB1s027.10H20,'vvhich comprisespreparing aso- Y lution or mixturecontaining Na20, B203 and H2O in proportions to give a compositionWithiny the about 51 C. and crystallizing said compound from saidsolution or m'ixtureatV a temperature above about 51 C.V Y

f HENRY BRUNO SUHR.

soY

